Thermal responsive device



' Nov. 6, 1945. F. R. HIGLEY THERMAL RESPONSIVE DEVICE Original Filed April 19, 1941 INVENTOR. 'EQAN/(E ///64 E y I ATTORNEYS Reissued Nov. 6, 1945 Frank R. Higley, Cleveland Heights, Ohio, assignor to The Bryant Heater Company; Cleveland, Ohio, a corporation of Ohio Original No. 2,290,963, dated July 28, 1942, Sam No. 389,401, April 19,1941. Application i'or'reissue July 24, 1949, Serial No. 498,095

V 4 Claims. This invention relates to improvements in compensated'thermostatic elements, that. is to say thermostatio'elements which are independent of ambient temperature and dependent for actuation upon the application of localized heat. Thermostatic elements of this character are commonly employed in connection with pilot controls for fluid burners, being responsive to heat from the pilot to operate a valve, an electric switch or I other shii'table control member.

One oi the objects of the invention is the provision of a thermostatic element of this kind which may be formed from regular stock material at a minimum of expense.

Another object is the provision of a thermostatic element oi the character described which shall have a relatively large flexure under the influence of applied heat and shall thereby be adaptable to a widened range 01' applications. Y

Other objects and features of novelty will appear as I proceed with the description of those embodiments of the invention which, for the pur-- poses of the present application, I have illustrated in the accompanying drawing in which:

able to exert less force than the flat strip elements now in more or less common use.

I In Figs. 1, 2. and 3 of the drawing I have shown a thennostatic element ill formed from a length ,of solid rod which is circular in cross-section.

, The circular cross-section is utilized partially because it is a common commercial product, al-

- appear.

though there is a further reason as will presently The material best suited for the purpose is a high quality stainless steel, since it is important that the element be capable ofresisting corrosion and of maintaining its elasticity indefinitely under repeated heating to a comparatively high temperature.

As illustrated in these figures the rod is provided near one end with a longitudinal slot- H the rod after which the rod is turned over and acut is taken from a point opposite the first cut. In this manner tapered ends l2. are formed at the extremities of the slot, thereby eliminating .the weak spots which would otherwise be presented by the junction of the slotted and solid Fig. 2 is a side elevation of the same, portions trate the invention;-

Fig. 4 is a transverse section taken on the line 4-4 0! Fig. 2;

Fig. 5 is a transverse section of a modified form of the invention;

and

Fig. '7 is a detail sectional view taken substantially on the line 1-1 of Fig. 6.

Compensated thermal elements as heretofore produced and used have been constructed in some cases of flat plates or strips of material provided with perforations extending lengthwise of the element so as to interfere with the transmission 'of heat crosswise of the strip. Such an element flexes in a direction parallel to its greater crosssectional dimension and is adapted to perform relatively heavy work, but it has a stroke of very limited extent. The thermostatic element of the present invention on the other hand has a re]- Fig. 6 is a plan'view of another modified form, r

atively long stroke, but its flexure takes place in a plane at right angles to its greatest crossdimension and the element is. therefore ie parts, and reducing possible breakage. With respect to cross-sectional dimensions, the slot II is shown centered midway of the rod, but it may be desirable in some instances to offset it fromthe median position. Its length may be varied.-

The parallel members formed .by the slot are marked Sin the drawing.

Points at which heat may be applied to the rod on one side of the slot are indicated by the arrows IS in Fig. 3. However, a single flame may be used instead of two flames, or the number may be increased to three or more. Obviously, variations in the length of slot used may call for a variationin the number of flames employed. In

any case to get maximum deflection of the rod it should be heated more or less evenly along one of the walls opposite the slot. The number and size of the flames will naturally be regulated to produce a maximum effect throughout the length of the slotted portion.

One end of the rod is fixed as indicated at ll in the drawing, a set screw being illustiated for the purpose at IS. The other end of the rod may be'formed for a convenient connection with some suitable control element. As shown herein, 1 may cut away opposed surfaces to form a flat extremity l6 and may bore a hole therethrough for a pivot pin or the like, not shown, to constitute part of the control connections. When heat is applied as at'points IS in Fig. 3 to one member Q! 2 3x member expands and puts a.

curve into that portion of the rod, which accomlishes a deflection of the free end as indicated to an exaggerated degree in the drawing.

of said solid and slotted portions having a sradually varying cross sectional area, whereby Fig. 4 shows a cross-section of a rod like that of Figs. 1 to 3, inclusive. The member or wall portion-on each side or the slot is a segment of a circle. The mass in each segment is equally divided by an axis A which is closerto the inner wall of the segment than to its outermost point. In Fig. 5 where the cross-section of a rectangular rod is shown, the masses in the members on D- posite sides of the slot are divided equally by axis lines A and A. If the width of the r0d\0f Fig. is the same as the diameter or the rOd a: Fig. 4, the lines A will we further apart than the lines A The mean fiexure of each wall portion takes place in what are originally planes through these lines A and A. Since the distance between the lines'A is less than that between the lines A the'flexure of the round rod will be sharper or on a smaller radius than that 01' the rectangular rod. Hence the round rod presents some advantages over the rectagular one. The width of the slot as compared with the diameter or width dimension ofthe rod may be varied more or less.

The construction of Fig. 6 diners from that of Figs. 1 to 3 in that the slot l8v is cut through one end of the rod' and the members. on opposite sides 01 the slot are caused to straddle a mounting projection iii to which the membersmay be welded, or if preferred, the projection may be drilled to receive rivets 20 or the like extending through aligned holes in the rod walls, as illustrated in the drawing.

the localization of stresses at the said Junction will be minimized.

2. A thermall responsive device comprising a metal rod having a longitudinal slot therethrough extending from one end or the rod to a point substantially removed from the opposite end thereof, leaving a pair of leg members disposed alongside each other on opposite'sldes of said slot, and bracket meansinterposed between the leg members atv the first named end of the device and secured thereto for mounting them in spaced 1 relation.

3. Athermally responsive device comprising a metal rod symmetrical about a plane through its axis, having a longitudinal slottherethrough extending along said plane from one end of the rod and terminating at a point substantially 'removed from the other end to provide two similar leg members projecting from and integral with the solid end portion, and. mounting means at Having thus described my invention, I claim:

the outer ends of said leg members, said members being secured to said mounting means, whereby the device is rigidly supported and movement will result from a difference in temperature between the two members.

4. A thermally responsive device comprising a metal rod having a longitudinal slot therethrough extending from one end of the rod and terminating at a point substantially removed from the other end, leaving two integral parallel members projecting from and integral with the solid end portion, one on each side of the slot, mounting means filling the slot between the outer ends of said parallel members, and means for fastening 7 said members to said mounting means, whereby the device is rigidly supported and flexure will result from a difference in temperature between 40 the two members.

FRANK R. HIGLEY. 

